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International Journal of Aquaculture, 2014, Vol.4, No.11 67
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the observed infestation) and
N. rufipes
(28.0%),
infested a high proportion of the dried fish sold (Osuji,
1974). Losses caused by
D. maculatus
infestation are
enormous. They include physical loss whereby the
amount of fish available for human consumption is
reduced, economic loss whereby the physical loss
despite the amount of fish available for sale and/or the
price commanded for insect damaged fish is below
that for undamaged fish, and nutritional loss, which is
a direct consequence of the physical and economic
losses and causes the retail value of fish to increase
beyond the purchasing power of the poor (Moses,
1992). Although many synthetic chemicals are
effective against the pests of many stored products,
but efforts to reduce losses through insect infestation
on smoke-dried fish by the use of insecticides and
pesticides have not been fully adopted due to the
hazardous nature of these chemicals to health and
toxicity at high doses to users (Balogun, 1992); higher
costs and less susceptibility of dermestid larvae
(Amusan and Okorie, 2002; Odeyemi et al., 2000).
Several attempts have been made by man to control
beetle infestation in cured fish and therefore mitigate
the food, economic and health losses caused by them.
Currently, worldwide interest is centered on the
development of alternative strategies, including the
re-examination of using plant derivatives against
agriculturally important insect-pests. It was reported
that when dried fish was mixed with leaf, bark, seed
powder, or oil extracts of selected plants, there was
mortality of beetles, reduced oviposition rate,
suppression of adult emergence and reduced fish
damage rate (Don-Pedro, 1985; Don-Pedro, 1989;
Adedire and Lajide, 1999; Weaver, and Subramanyam,
2000; Okonkwo and Okoye, 2001; Anyaele and
Amusan, 2003).
The plant
Phyllantus fraternus
is a pan tropical weed
which belongs to the family Euphobiaceae (Mehta et
al. 2013). It is
known for its hepatoprotective
properties (Rastogi and Mahrotra, 1990)
. The plant is
a common weed of cultivated fields;
found abundantly
in rainy season (Khan and Khan, 2004)
and spreads
widely in West Africa and other parts of the world
where they are employed widely in traditional
medicine preparations (Umoh et al., 2013). In Nigeria,
it is known among Ibibios and Efik’s as ‘‘oyomokiso
aman ke edem’’, Yoruba as “eyin olobe”, Hausa as
“geeron tsutsaayee” and Igbo as “Ite knwonwa nazu”
and in English as “leaf flower” or “chamber bitter”
(Etukudo, 2003; Okujagu et al., 2005). It
is usually
used as infusion and drunk by Nigerians for health
maintenance and it is considered as a wonder-
working herb and has great economic importance
(Etukudo, 2000) but the insecticidal properties are not
yet to the exploited.
Therefore this present study aimed at determining the
phytochemical and larvicidal activity of powder of
this medicinal plant in order to evaluate its insecticidal
potential in suppressing infestation and damage by
D.
maculatus
on stored smoke-dried fish.
1 Materials and Methods
1.1 Experimental location
The study was conducted at the Biology Laboratory in
the Department of Science Laboratory Technology,
Rufus Giwa Polytechnic Owo, Ondo State, Nigeria (7°
11' 43'' N 5°33' 57'' E) under ambient condition of
30±2°C temperature, 65% relative humidity and 12L:
12D photo regime.
1.2 Collection and Preparation of leave powder
Whole plant of
P. fraternus
was collected from
within the polytechnic community and the identity
of the plant was confirmed at the Forestry and Wood
Technology Department of Rufus Giwa Polytechnic,
Owo, Ondo State, Nigeria. The plant material was
shade dried for two weeks, and thereafter milled
using an electric grinder and sieved to pass through
1 mm
2
perforations.. The plant powder was kept in a
separate sterile plastic container and placed in a
cool dry place for use.
1.3 Insect culture and maintenance
The initial source of
D. maculatus
culture used for this
study was obtained from natural infested smoked
catfish
(C. gariepinus
) collected from smoked fish
market stall in Owo, Ondo State, Nigeria. It was
maintained in a kilner jar covered with muslin cloth
under laboratory conditions and kept at a temperature
30+ 2
℃
under relative humidity 65 + 5%. All
bioassay jars was disinfected in an oven at 80
℃
for 2
hours and were allowed to cool at room temperature.
New generation was prepared by removing newly
emerged (0-72h old) larvae from a stock culture, and
placed on fresh uninfected fish, while the parent adult
was removed after 2-3weeks oviposition period.